Crash management systems and crash structures form a significant part of modern vehicle design. A vehicle structure is typically made up of two zones, the passenger compartment/cell and crumple zones, as illustrated in FIG. 1 for two examples, namely automotive vehicles and railway vehicles where in each case ma and mb represent the masses for vehicles A and B and ka and kb are the corresponding stiffness values for the crumple zones, respectively. The passenger compartment is the region in which the passengers are located, with this being designed to remain rigid/stiff, hence, preventing intrusion of other vehicles into the passenger compartment. The crumple zones are typically located at the front and rear of the vehicles for energy absorption in the event of a frontal or rear end collision, hence these are designed to fail in a controlled manner. The zones of the vehicle are herein referred to as crash structures. The term crash structure refers to both regions of a vehicle such as the crumple zone and passenger cell, as well as the components of these regions which absorb collision energy.
Relevant safety standards typically require a vehicle body to be able to withstand an impact with a stationary structure. However, many collisions occur between two or more vehicles. Furthermore, such vehicles may be of differing mass. For example, in a collision between a small car and a sports utility vehicle (SUV) the difference in mass between the two vehicles may be over 2 tonnes. The difference in vehicle mass in a collision may lead to the larger vehicle absorbing less energy than a smaller vehicle, which is manifest as aggressivity of the larger vehicle over the smaller.
It is known that certain materials, known as actively controlled materials (ACM), commonly referred to as smart materials, such as magnetorheological materials, piezoelectric polymers, shape memory alloys etc., can adjust their stiffness. The timescales in which the adjustment occurs is of the order of 50 ms or less. Such materials can therefore be used in vehicle crash structures (such as the front or rear end crumple zones) where the stiffness of the structure can be adjusted in the event that a collision is about to occur, i.e. adjustment is made in advance of the collision. For example U.S. Pat. No. 7,046,167, in the name of Ford Global Technologies, describes a system in which the stiffness of a vehicle changes in the event that a collision is predicted to occur. Existing systems, however, do not consider the other vehicles involved in the collision.
Accordingly to mitigate some of the above problems there is provided a method of managing collisions between a plurality of vehicles in an active collision management system, wherein one or more the of the vehicles has a crash structure whose stiffness can be adjusted and one or more object detection sensors, the method comprising the steps of: determining whether a collision event between the plurality of vehicles is to occur based on data measured by one or more object detection sensors; and in the event that a collision event is to occur, for a first vehicle involved in the collision event: identifying a first crash structure and determining an initial stiffness of the crash structure; and subsequently determining a level of aggressivity of the collision based on a predicted energy absorption as a result of the predicted collision for each of the plurality of vehicles; determining a subsequent stiffness value for the first crash structure based on the predicted energy absorption and level of aggressivity of the collision such that the energy absorbed by the crash structure is changed and the level of aggressivity of the collision is reduced; and adjustment of the stiffness of the first crash structure to the subsequently determined stiffness value. An aspect of the present invention is that there are a plurality of controlled stiffness values of the crash structures amongst the imminently colliding vehicles. This is realised via vehicle-to-vehicle and vehicle-to-vehicle (V2X) communication and exploitation of a decision maker linked to a multi-dimensional look-up table (MDLT) and nonlinear interpolation of stiffness values using fuzzy logic.
Such a system therefore allows for one or more vehicle(s) involved in a crash to compensate for the differences in vehicle masses and reduce the aggressivity of the collision. By predicting the amount of energy to be absorbed by each crash structure in advance of the collision, the stiffness of the crash structure can be adjusted so the energy absorption may be distributed more fairly between the vehicles in the collision and the overall aggressivity of the collision is reduced.
Other aspects of the invention will become apparent from the appended claim set.